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' reacted Mar. 13, 1945 iJNlTED .STATI-:s tnrlzurormcs ELECTRIC CONTACT Franz R. Hensel, Kenneth L. Emmert, and James W. Wiggs, Indianapolis, Ind., assignors to P. 1R. Mallory & Co., Inc., Indianapolis, Ind., a corporation of Delaware Application May 27, 1943, Serial No. 488,7/16

4 Claims. (Cl. 20D-166) This invention relates to electric contacts.

An object ofthe invention is to improve electric contacts and the composition thereof.

Other objects of the invention will be apparent from the description and claims.

In the drawing Figure 1 illustrates a contact combination 'formed of contacts of the present invention and Figure 2 shows a contact combination in 'which one of the contacts is of the composition of the present invention and the cooperating contact is formed of another material.

The present invention contemplates an electric contact formed of an alloy containing gold, silver and one or both of the metals cadmium 'and zinc.

The ingredients may be present in the following ranges of proportions, by weight:

. Per cent Cadmium, zinc or cadmium plus zinc-- 0.5 to Silver 1 to 50 Gold t0 98 Small proportions of other ingredients, such as copper, platinum, palladium, nickel, cobalt, indium, tin, may in -some cases be present. These materials, if present, may be substituted for an equal proportion of silver in proportions of 0.1 to 20% of the alloy. n

Alloys of gold, silver and cadmium form the preferred contact material.

The preferred composition range is Per cent Cadmium i to 15 Silver 3 to 30 Gold Balance The following specic contact materials have been found to be very satisfactory.

The'contact alloys are readily produced by contion range of gold-silver-cadmium. It has been found advantageous to have a homogeneous matrix since this will assist greatly in decreasing the tendency to either Welding of vcontacts or material transfer.

The present contact materials made of gold base alloys'have the disadvantage of high material transferY usually in the form of needles. Such needles will result in ultimate failure of the contacts since the needles will cause a mechanical interlocking into the crater of the mating contact. The improved alloys of the present invention eliminate these ldifficulties and thereby provide contacts which can be operated for long periods of time. The noble characteristics of the t alloys permit operation at extremely low contact pressures without creating films on the contact surfaces resulting in high contact resistance. The alloys are also applicable to control equipment which has to operate in industrial atmospheres usually contaminated with sulfur since they will resist tarnishing or corroding.

In certain D. C. applications it has been found advantageous to operate the contacts of the present invention against a differential contact material such as a silver base, platinum and/or palladium base or a, refractory base composition. The refractory base metals may be either swaged tungsten compositions or Elkonites which are compound metals having a refractory base and containing lower melting .point materials such as copper, silver andgold.

I Figure l of the 'drawing shows a pair of cooperating contacts I and 3 both formed of the alloy of the present invention brazed or welded to support arms 2 and 4 respectively. Figure 2 shows contact 6 formed of the composition of the present invention mounted on support arm 6 for cooperation with another contact 'l formed of another composition mounted on .support arm 8..

While specific. embodiments of the invention have been described, it is intended to cover the invention broadly within the spirit and scope of the appended claims.

' What is claimed is:

1. An electric contact formed ci an alloy ci 0.5

` to 20% of an element selected from the group ventional alloying methods, including standard g r melting procedures, manufacture by powder metallurgy.' plating. and subsequent diffusion etc. The compositions moet suitable for electrical contact purposes fall within the ternary solid soluconsisting of cadmium and zinc, 1 to 50% silver and 40- to 08% gold.

2. An electric contact formed of an alloy of 1 to 15% cadmium, 3 to 30% silver and the balance gold.

3. An electric contact formed of an alloy of 3% cadmium, 25% silver andthe balance gold.

4. .An electric contact formed` of an alloy of 10% cadmium, 20% silver and the balance gold.

, FRANZ R. HENSEL. 

